DeRosa,
Basically a showcase is an event where baseball players with the ability or potential to play college or pro ball, go and compete or showcase their talents against other talented players. Good showcases are attended by college coaches and recruiters, and pro scouts, who then follow the players they are interested in, and eventually may offer them scholarships, or draft them.
You can learn a lot more about showcases by reading the other threads in this forum. You might also want to visit the websites of a couple of the reputable showcase organizations who participate in this message board:
www.perfectgame.org (a large, well known scouting organization based in Iowa, but they hold many large and small events around the country and have a close relationship with Baseball America), and...
www.collegeselect.org (another well-respected organization based on the East Coast; the owner TRHit participates in this board and has good contacts with many college coaches).
To determine what your skills need to be, you might contact one of the showcase org's, or just read some of the player profiles from their previous events (listed on their websites). Hope that helps a little!