Complex sentence: Registered and non-registered trademarks are both eligible for protection under the Lanham Act, but the advantage of having a registered mark is that after five years of unopposed use, the mark becomes "incontestable".
Split into simpler sentences: Registered and non-registered trademarks are both eligible for protection under the Lanham Act. The advantage of having a registered mark is that after five years of unopposed use, the mark becomes "incontestable".