I often hear escort cards and place cards used interchangeably ( I myself am guilty sometimes)! Here is the breakdown. An escort card is the card that is picked up as you enter the reception. That card will have your name and your table assignment. You place card is a card on the actual table that lets you know what seat is yours.
The great thing about escort and place cards is that they actually do not have to be "cards". You can combine either with favors or any other trinkets that follow your theme. You can also change up your escort card table by displaying them in a creative way. Picking cards out of trees or out of beds of grass introduces your guest to what obviously will be a reception to remember.
Display boards are also becoming popular. It's a great way pull in the color and theme of your wedding. It can be used as just a reference board or guests can pick off their card.