In 18c, most of the music was composed for Church and Dancing which to coordinator the dancer and singer. During that time, music always needs to feel Inner pulse between every beat which requires the style of music playing. Sound release was the character for this typical music style, which means not fully legato between the long notes that creates a rest between every beat.
Mordent is a music ornament which indicating that the note should play an alternation between written note and single note above or below in fast tempo. In 18c, mordent had two different types of mordent, pralltriller which indicate the mordent notes start below the written notes and Schneller which start from above the written notes.
Trill is a musical ornament consisting of a fast alternation between two notes, provides rhythmic, melodic, and harmonic interest. In18c, the details of trill of how to play the trill are up to the performer which every performer has to follow the ornaments rules from composer during the performances. In general, trills in this era are beginning on the note above written note, often producing the effect of a harmonic suspension which resolves to the principal note.