I lived a happy life without ever tinning, for the first few years after I started exploring electronics.
But it can help.
To “tin” is to apply a bit of tin to something.
For example – you can tin the tip of your soldering iron by first cleaning it with a sponge, then apply a bit of solder to the tip.
Or you can tin the pin of a component by heating it with your soldering iron, then melt a bit of solder onto it.
The advantage is that it will transfer heat better.
So when you tin the tip of your soldering iron, it should make the soldering process a bit simpler.
When I solder, I regularly clean the tip with a wet sponge, then tin the tip before continuing.
Tinning the tip of your soldering iron before you put it down for the day is said to help your tip last longer.
If you’re new to soldering, learn to solder in my eBook «Getting Started With Electronics»:
Keep On Soldering!
Oyvind @ build-electronic-circuits.com