The Five Love Languages is a book by Gary Chapman that describes the five primary ways people give and receive love. The author of the book has used it in relationship counselling for many years, and has had good results.
Words of affirmation: people saying nice things about them, complimenting them, thanking them for doing things, etc.
Physical touch: can range from a pat on the back, to cuddling, to sex, depending on the context
Quality time: just spending time with the person. Maybe it’s hanging out with a friend for 2 hours at a coffee shop, maybe it’s a weekend away with just your spouse.
Acts of service: somebody doing things for you. It could range from a spouse making you breakfast, to a co-worker cleaning your office, to anything in between.
As a side note, it’s very important to remember that “love” as talked about in the book, does not just mean romantic love. It means receiving affection of any kind, or even respect. It can be entirely platonic, or familial, or romantic, or whatever else. Regardless of the relationship, certain “gestures” mean more to you than others.
Anyway, back to the main topic. Basically, different people “speak” the five different languages to a greater or lesser degree. For some people, they really feel loved by physical touch. When they are away from home all day, the first thing they want to do when they get home is kiss their spouse. Other things don’t matter as much to them: they don’t really need compliments to feel good; they don’t care if their spouse never takes out the trash or makes them dinner. But if they don’t get to cuddle every day, they start to feel cold and grumpy and miserable.
Some people “speak” more than one language. A woman might really love getting gifts from her boyfriend – even stupid, tiny gifts like a magazine because he was at the corner store and picked it up for her – and it really means a whole lot when her assistant handles little things for her at work, like checking the messages on her phone (i.e. Acts of service). But for her, physical touch just doesn’t matter that much. Sure, she enjoys sex, but if she goes without for a week or so it isn’t going to be emotionally devastating.
If you’ve wrapped your head around this so far, next comes the important part: figure out which languages your partner “speaks”, i.e. which ways of receiving love matter the most to them, and do those. Maybe your wife really loves receiving gifts, no matter what they are. You don’t really care about gifts at all, but you really crave words of affirmation. You need to get it into your head that when your wife hears you say “Oh, I bought you some flowers on the way home from work”, it’s comparable to you hearing “You are the most wonderful man I know, and I am so glad I married you.”