TKIP (Temporal Key Integrity Protocol) and AES (Advanced Encryption Standard) are different encryption protocols that can be used with WPA. TKIP is the method that was called for in the original WPA specification. AES, which is even more secure, was added as an alternate method to later versions of the specification. So, if the network uses WPA, but doesn't specify which of these it uses, TKIP is the most likely of these to be supported by the network.