Sequence alignment involves arranging biological sequences like DNA, RNA, or proteins to identify similar regions that may indicate functional, structural, or evolutionary relationships. There are two main types of sequence alignment: local alignment, which finds short, locally similar regions; and global alignment, which tries to match the full sequences. Sequence alignment is performed using algorithms like Needleman-Wunsch for global alignment and Smith-Waterman for local alignment. It can provide information about sequence homology and evolutionary relationships between sequences.