What is e-value of an alignment?

The e-value (expectation value) of an alignment in bioinformatics represents the number of alignments with a score equal to or greater than the observed score that would be expected to occur by chance in a database of a given size. A lower e-value indicates a more statistically significant alignment, suggesting that the observed similarity is less likely to be due to random chance. E-values are commonly used in tools like BLAST to assess the quality of sequence alignments and their biological relevance.