There are lots of apps, desktop software, and websites. I prefer to use the default editor on openstreetmap.org called iD. Zoom in to your neighbourhood and click 'Edit' and it will open.
wiki.openstreetmap.org includes best practices and documentation for how to map each real world thing.
In iD, you can click on something in the map, on the left side it will tell you what type of feature it is. There will be a little 'i' symbol that you can click for more details and documentation that links to that specific type of thing on wiki.openstreetmap.org
community.openstreetmap.org is the place to ask questions and get help from others.
For actually using the map for finding places and getting directions, I like CoMaps best.
Any change is updated immediately. End users (apps) may only update every month or so, that's up to them.