Seek Predicate is the seek operation that uses the b-tree part of the index to find matching rows.
Before SQL Server can perform an index seek, it must determine whether the keys of the index are suitable for evaluating a predicate in the query.
For T-SQL example and explanation check flowing post
A predicate is an exp ression that evaluates to True or False or filter using non key column.
In SQL you encounter predicates in joins and in WHERE or HAVING clauses, where they are used to either filter out or qualify rows.
Here's a query with two filter predicates:
SELECT * FROM ScoreCard
WHERE Marks > 60 AND DeletedDate IS NULL
And a query with one join predicate:
SELECT * FROM FirstTable
INNER JOIN SecondTable ON FirstTable.column1 = SecondTable.column1