Flatpicking is a style of guitar that uses a pick to strike the strings, as opposed to using the fingers in fingerstyle. It's used a lot in bluegrass style music, but has moved into other genres as well.

There are several techniques used in flatpicking, including:

Alternate picking is a guitar playing technique that employs alternating downward and upward strokes in a continuous fashion. If the technique is performed at high speed on a single string or course voicing the same note, it may be referred to as 'tremolo picking' or 'double picking'.

Crosspicking is a guitar technique in which a flatpick is used to play a rolling, syncopated pattern across three strings. This rolling pattern typically outlines chord tones; however, melodic lines can be featured as well. The crosspicking technique was developed to imitate the sound and aesthetic of a banjo roll, with the primary difference being that banjo rolls are fingerpicked rather than flatpicked.

Sweep picking is a guitar playing technique. When sweep picking, the guitarist plays single notes on consecutive strings with a 'sweeping' motion of the pick, while using the fretting hand to produce a specific series of notes that are fast and fluid in sound.

Economy picking uses both alternate picking and sweep picking. When playing notes on the same string alternate picking is employed. When moving up or down on consecutive strings sweep picking is used. Generally, alternate picking is used when moving along the same string, sweep picking is used arpeggios.

These are not the only flatpicking techniques, but they do offer a good starting point.