A book launch is events you create to introduce the book to the world around the time of the publication date.
Book launch parties and book signings are much less common than they once were. Unless you have an active publicity campaign, it is hard to get enough people to a bookstore signing to make it a good sales opportunity. You have a better chance at generating sales if you give a talk or seminar and have back-of-the-room sales there.
Your local independent bookstore is your best chance of a book signing, if that is important to you. Get to know the manager before your book comes out and find out how the process works at that store.
More and more authors are creating virtual book launches and launch events, including email campaigns and getting noticed by bloggers and interviewed by podcasters.
A word to the wise: Plan some fun at the events surrounding your book launch. You have worked hard to create your book, so enjoy the process.