What does John 1 3 talk about? What does 1 John Chapter 3 mean?

Chapter 3 further discusses the importance of being a child of God and living accordingly (3:1–10). A major implication of being a child of God is that we are to love one another (3:11–24).
My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous:

2And he is the propitiation for our sins: and not for ours only, but also for the sins of the whole world.

3And hereby we do know that we know him, if we keep his commandments.

4He that saith, I know him, and keepeth not his commandments, is a liar, and the truth is not in him.

5But whoso keepeth his word, in him verily is the love of God perfected: hereby know we that we are in him.

6He that saith he abideth in him ought himself also so to walk, even as he walked.

7Brethren, I write no new commandment unto you, but an old commandment which ye had from the beginning. The old commandment is the word which ye have heard from the beginning.

8Again, a new commandment I write unto you, which thing is true in him and in you: because the darkness is past, and the true light now shineth.

9He that saith he is in the light, and hateth his brother, is in darkness even until now.

10He that loveth his brother abideth in the light, and there is none occasion of stumbling in him.

11But he that hateth his brother is in darkness, and walketh in darkness, and knoweth not whither he goeth, because that darkness hath blinded his eyes.

12I write unto you, little children, because your sins are forgiven you for his name's sake.

13I write unto you, fathers, because ye have known him that is from the beginning. I write unto you, young men, because ye have overcome the wicked one. I write unto you, little children, because ye have known the Father.

14I have written unto you, fathers, because ye have known him that is from the beginning. I have written unto you, young men, because ye are strong, and the word of God abideth in you, and ye have overcome the wicked one.