1. Global alignment finds the optimal alignment over the entire sequence length trying to match as many elements as possible, while local alignment finds the region of highest similarity between two sequences that may be of different lengths. 2. The Needleman-Wunsch algorithm is commonly used for global alignment using dynamic programming to find the optimal full sequence alignment with linear gap costs. 3. The Smith-Waterman algorithm is used for local sequence alignment to identify similar regions by calculating similarity scores and only retaining alignments with scores higher than a threshold.