Welcome, @Heulog.
What DoctorTwo said is absolutely right, there’s no right or wrong way to play the game and if you just want to ‘catch em all’ then go for it.
However, if you want to fill your dex then you might need to know a bit about eggs and raids as some Pokemon are exclusive to those methods.
So, eggs are simple, go to your Pokemon screen and swipe right. Eggs you’ve collected from stops will be there (you can also get eggs via gifts from friends) pop an egg in an incubator and when you’ve walked the set distance it will hatch a mon.
Raids happen at gyms, some raids are easily achievable alone some require a group of people. Click on the gym when the raid is in progress, use a pass and tap like your life depends on it. If you win you get a chance at catching the boss. There is more to it than that, such as having the best counters etc, but if you start with 1 & 2 star raids to get the hang of it there’s no need to worry about that yet.
IVs are the Pokemon’s ‘DNA’. To find out the IV of individual mons you need Pokegenie or a similar third party app. The app will do all the calculating for you, most people consider anything below around 90% IV to be a bit pants. But again, that depends on the player and for the more useless Pokemon it’s largely irrelevant anyway. Your not going to use a Spinda in battle whether it’s 100% IV or not! Nice to have though 