The temples of Goa are in essence like most Hindu temples in India, based around a deity which is worshipped. The architecture of Goan temples is a little different mostly because of historical reasons.
The fundamental design of any Hindu temple is organized around the central shrine or the "Garbagriha" or the "sanctum sanctorum" that houses the main deity. A tower or "Shikara" arises from the main shrine and is traditionally pyramidal shaped. There are usually two or more smaller shrines housing other deities known as "Parivar Devatas" around the entrance to the Garbagriha.
There is always a surrounding free area or a passage around the Garbagriha that is kept free for a an essential Puja ritual known as "Pradakshina" performed by almost every devotee. This is the ritualistic left sided circum-ambulation around the shrine usually an odd number of times.
The "Garbagriha" is accessed via a large hall with pillars and walls either carved with religious motifs or scenes from the mythology pertaining to the deity. This hall is usually known as the "Mandapa".
The "Mandapa" opens to the outer courtyard or "Prakara" where usually a statue of a mythical animal or Vehicle of the deity is placed. There may also be a sacred plant the "Tulsi" or one of the sacred trees usually either a Pepul or a Banyan tree with some small artifacts or statues of more deities at its base.