What is a showcase? Steem

Steam level function; Add Amount in friendlist + 5 friends per level. (for example, steam level 1 max friends 10. after level 2 increase friendlist will increase to 15)
Getting Showcases for Steam Profile (Each goes 10 levels, then you get 1 showcase)
What is a booster pack?
Increase the chance drop booster pack (+ 20% chance every 10 levels) Booster pack is a term that is already commonplace in the world of trading card (Yugi, Vanguard, etc.)
Booster pack is 3 trading card contents.
Card contents in this pack can be normal card or foil.

How to get a booster pack?

If the specific game card has dropped everything then you will get eligible status for booster pack.
Keep in mind that the booster pack is dropped at random (random time) once a week per game. yep "per game" If you are lucky could have 3 booster pack at once.