How to create a procedure in Firebird to search for a row in a table?

Question

SQL

Good afternoon, I need help with creating a procedure for Firebird (Version 2.5, if it is important), which will search for a row in a table after the user enters some data into the text field of the program (with interaction with the procedure from my program I figure it out myself). In this stored procedure, the input parameter should be a variable with the text to search for, and the output parameter should be a found string or variable of some type. I would be grateful for both explanations and just ready-made code, but please accompany it with at least brief comments, because I want to really understand, and not just copy. Thank you!