You have already been given very good advice. To further explain the letters behind "22", for many years shooters were given the option of buying shorts, longs, or long rifles for their guns. The terms come from the length of the cartridge, or brass. The shorts were, naturally, the shortest of the bunch, and contained less powder than the other two. You also had to be careful that the gun you were shooting was chambered for the length cartridge you were shooting. You can shoot any regular .22 ( short, long, or long rifle) in a .22 lr chambered gun, but you cannot shoot an lr in a gun chambered for .22 short.
I believe on today's market, the long rifle chambering is used exclusively, and by far .22 lr ammo is pretty much the standard round. I can still buy .22 short ammo if I want a little less noise, but I can't remember seeing .22 long ammo for many years. I do believe that CCI makes a .22 long and .22 short round, but I think they are used mostly for backyard pest control where quiet is a must.
Hope this gives you a little better insight as to some of the nomenclature used. If I missed anything here, I'm sure one of the other guys will help point it out
Good luck with your choices, have fun, and most of all, BE SAFE!!!