What is the difference between all of these "cards", and do you need them? For more formal dinner receptions, guests are often assigned to tables. Once the RSVPs are in, you'll plan a seating chart, deciding who will sit with whom and where in the room you'd like everyone. While it's often easier for you to let guests sit where they choose, and it lends to a more casual atmosphere, I do believe that wedding guests appreciate being told what to do and where to go, especially in large numbers.
Escort cards are positioned (and many times, alphabetized) near the entrance of the reception and list guest names and the table they're assigned to. Table cards sit on the dinner table and show the number (or name) of each table. This part is really important. Many brides choose to name their tables with words, places, or things that are important to the couple or theme of the wedding. Print your table names clearly! Lighting is typically dim in reception rooms and your guests have a hard time finding their table name when they don't have a floor plan and the name is written in a small, cursive font. I recommend filling at least a 4x6 card with the table name, and don't use a script unless it's large and easy to read. To up the formality a bit more, place cards are positioned on dinner tables to assign a seat to each guest. This tradition is often skipped these days, but can be helpful to banquet staff or caterers if guests have pre-chosen their entree on their response card. It also allows you to be thoughtful in your seating plan, placing important people where they can easily see the dance floor, for instance, or playing matchmaker and seating your single friends side-by-side.
Here are some great ideas for escort, table, and place cards: