To be honest, I tend to use the description "Christian" as seldom as possible! The reason is that I find that the word has been so totally devalued! You may have experienced this for yourself! "Mrs McTavish, across the street - what a wonderful woman! She would give you the coat off her back; she would give you her last slice of bread; she would walk twenty miles to help you; she's a good Christian"! Now, if I knew this mythical Mrs McTavish, I have no doubt that I would consider her to be a very nice person; the "salt of the earth"; someone who would be good to have as a next-door-neighbour. Sadly, however, that does not make her a Christian! A Christian should be like that - and much, much, more - but that is another story!
The fact remains that many people think that they are "Christian" because, they would claim, they are not 'pagan' and, of course they were 'born in a Christian country'! Their names may even be on the membership list of a Christian fellowship which they attend occasionally, and to which they sometimes provide financial support (even if somewhat meagre!). However, it takes more than that for a sinner to become a child of the living God. It takes repentance from sin, and faith in the Lord Jesus, the Christ, Who gave Himself as an atoning* sacrifice on the cross at Calvary, and Who rose again that we may have eternal life - a life that has much more to do with quality than longevity!
So, back to the title question - what is a Christian? The word was first used by the people of Antioch, and was really a term of derision! These were "Christ-followers" and, as such, were deemed to be somewhat crazy! But certain things may be said about them that we may use to see if we measure up to what it required.
They were, and are, those who know a Person - and that Person is the Lord Jesus, the Christ. Of course, many know about Him - but this is a personal knowledge. If I may explain it like this - I know HM the Queen, and have been, on more than one occasion, no more than eight feet away from her! I know her date of birth - both biological and official; I know her husband's name; I know her children's names - and those of her grandchildren and even great-grandchildren. I know when she became Queen; I recall her Coronation; I know her favourite animal pet; etc., etc. Anything that I don't know, but wanted to, I could easily find out online!
I also know my wife! But that 'knowledge' is totally different. It's a knowledge that has come from now more than fifty years of marriage - and a couple of years of courtship before that! It's the knowledge that comes from an intimate relationship that has deepened over the years. It's a knowledge that comes from shared experiences, and of seeking to put her first (even if I haven't always managed to do that!).
Do you see the difference. In the case of HM the Queen I know about her. When it comes to my wife - I know her! And it's that kind of knowledge of the Lord Jesus that His true disciples have.
But not only do we know His Person; we also enjoy His presence. Have you ever been involved in a "long-distance" relationship? I don't recall ever having been, in the past - but I am experiencing it at the present time. Because of the current situation regarding Covid-19, I have not seen my children for a full year! Oh, we communicate regularly, using the various forms of modern technology to which we have access. We share our experiences; at times, we rejoice with one another; on other occasions, we commiserate with one another. But it just isn't the same as being able to hold one another in a big hug!
Jesus said to His disciples: "I will never leave you, nor forsake you." (Heb.13:5). His presence, through the indwelling of God the Holy Spirit, is with His disciples always. That even includes the experience of physical death. David, the psalmist-king of Israel knew this. In what is probably his best-known psalm, he writes these words: "Even though I walk through the valley of the shadow of death, I fear no evil; for Thou art with me;" (Ps 23:4). That is why death holds no terror for the disciple of Jesus - because his Lord is with him. On Wednesday of this week, I shall (D.V.) be conducting the funeral service for a friend of some seven years. There will be mixed emotions. On the one hand, his widow, extended family, and friends, will grieve. But - and it is a very big "But" - we shall recall the words of Paul to the Thessalonian disciples: "But we would not have you ignorant, brethren, concerning those who are asleep, that you may not grieve as others do who have no hope. For since we believe that Jesus died and rose again, even so, through Jesus, God will bring with Him those who have fallen asleep." (I Thess. 4:13-14). A presence that not even physical death can remove.
I know His Person; I enjoy His presence; and I experience His power. The life of a true disciple of Jesus is not always easy. Most of those who read this post will not suffer to the same degree as those in what we refer to as "the persecuted church". But there may be discrimination; ostracism; loss of former friends; even rejection by family. How does one cope with such situations? Just before He ascended to the Father, the Lord Jesus spoke to His disciples and, in that brief discourse, He made this promise: "... you shall receive power when the Holy Spirit has come upon you;" (Acts 1:8). Power to live; power to witness; power to suffer for His name's sake. All that we need is found in Him.
That, in a nutshell, is a description of a disciple of Jesus - a true Christian. Note, of course, that I used the indefinite article! That is because there is so much more that might be said concerning the subject. However, I trust that what I have shared in this post will help some to examine themselves, to see if they are, indeed, His disciples - or merely using the name. If you should conclude the latter, then I beg you not to procrastinate*. Deal with the matter now and, if I may be of any further assistance, feel free to contact me at the e-mail address at the top of the page.
* These words are dealt with, fully, in my first book: "Great Words of the Faith". Links to it and to the other two in the series, are at the top of the page. Remember that I am happy to promote my books because ALL royalties are sent, directly, to Release International, in support of the persecuted church.