GOP stands for “Grand Old Party”, which is a nickname for the Republican Party in the United States.
MAGA is an acronym which stands for “Make America Great Again”, and was used by Trump during his run for the presidency. It has since been used to indicate those that follow Trump and his policies.
Just to further clarify, MAGA was originally used by Ronald Reagan (and later Bill Clinton)… it’s just another thing recycled by the orange guy who has no ideas of his own.