When you look into a haiku, you are usually given a big history of the form. All you need to know is that there are 3 LINES IN TOTAL.
The first has five syllables.
The second seven syllables.
The third, five syllables once again.
Classically, haikus are about nature, but they can be about ANYTHING. You can make a diary of haikus to commemorate your days or link them together to tell a story. There are a lot of journals that call for them. Read a sampling of what they accept to get an idea:
Here’s one that is open right now for submissions: