hiii. ok this is gonna get kinda long but tldr it kinda depends on what you're looking for specifically and what area of the world you live in.

short answer: go outside and observe.

long answer:
i would start with the birds around you. in my experience it's a lot easier to remember things about the little guys that i see all the time. there are more birds than you think there are, you just have to pay attention.

if you just want to learn facts and you're in north america i would recommend allaboutbirds.org. you can search by zipcode and pull up a list of birds that are in your area, and it lists some id stuff and also some fun facts about them! very nice website i love it a lot

if you're in other parts of the world, i'm sorry, but i'm not terribly sure of any other good website that does something like that. you can try
- Merlin, an app for bird id which does have the ability to pull up a list of birds in your area, and then searching for facts on the internet
- birdsoftheworld.org is a good website with comprehensive information but unless you're really deep in the rabbit hole or actually working with birds it's probably too much detail / scientific paper stuff and also it has a subscription fee (but some universities, if you're in one, might give you institutional access)

biased here bc i run a bird club but going on a birdwalk with more experienced people is a) a good way to learn a ton of new facts and b) appreciate just how many birds there are out there. they will hear things that you don't even notice.

if you're learning how to id birds:
1. get merlin bird id it's free. do it.
2. go outside.
3. ???
4. profit
optional but very very helpful: get a pair of good binoculars (there's some online guides to picking out good ones for birders, but 8x42 or 10x42 are a good bet for magnification specs)

if you have a camera, posting pictures on inaturalist.org is good! or just scrolling through pictures there is really fun for me.

i'm not terribly good with bird id but i would recommend looking at shape and size over color because those stay more consistent.
some things to note that people don't think about:
- shape of the beak
- if there is a ring around the eyes or not
- overall behavior-- is it jumping around wildly, sitting still, on the ground, up in the trees?
- habitat: are you in a riparian area, open field, etc.

other than that just looking at pictures online and stuff. when i actively used tumblr i followed a blog called birdoftheday and one called birdsandherps and they would just post bird pictures and their common name/scientific name below. i think now there's also blogs like identifying-birds-in-posts or something like that.

you can also dm me / drop questions here / tweet at me abotu birds anytime if you have any specific questions. i probably won't know the answer but i'll also probably be able to find it.

sorry this got kinda long and frankly a little overwhelming. i think everything really does start from loving them and then going outside to see them. i got really into birds during 2020 when i was doing online school and a pair of house finches showed up constantly to steal the berries from a bush outside my window. be my bird friend. please. i love talking about birds