Sargable stands for Search ARGument Able. Sargable conditions help query optimizers to use the index defined on column(s) effectively. Sargable conditions have a higher chance of meeting index seek than index or table scan.
Writing a sargable condition is also a preventive step. Consider this factor while writing the query or while working on performance tuning projects. There are some operators that make your query sargable or non-sargable. Here is the list:
LIKEconditions that have a wildcard character as a suffix, for example,
FirstName LIKE 'R%')
LIKEconditions that have ...