Lets start at the begining... so what are they ?
Measuring aprox 1.0 to 1.4 meters in height Jawas are thought to be a evloved rodent like species. They dress from head to foot in rusty brown hooded robes and the only feature visable is their hands and glow of their eyes. Jawas commomly have leather bandoliers criss crossed over their shoulders and use rudamnetry ion weapons and equiment for restraining droids.
Jawas are scavengers and traders of droids and anything else that might pass their way. They are inhabbitants of the desert world of Tatooine and this rather skittish race lives in large velihcles called Sandcrawlers, which is protects them from Tusken Raiders and sand storms.
On film... Jawas first appeared in Star Wars Episode IV 'A New Hope'- released in 1977.
In the Jawas first scenes, they encounter and catch C-3PO and R2D2, which the Jawas fit both of the droids with restraing bolts and take them on board their Sandcrawler. Subsequently they meet up with Luke Skywalker's Uncle Owen and sell him both droids.
Later on, the same group of Jawas are found murdered by Stormtroopers who were also looking for the 2 droids.
Some other Jawas are also seen outside the Mos Eisley Cantina and another noteable appearance in Star Wars 'Return of the Jedi' where a Jawa in seen in Jabba the Palaice as a slave using a long fan.
A other Jawas are seen at the Pod Race scenes in Star Wars 'the Phantom Menace'