Swallows and Swifts, the two near identically looking birds swirling in the air, are often confused due to their similar appearances and aerial lifestyles, but they belong to different bird families and have distinct characteristics:

 Swallows have longer, more pointed wings but are less agile than swifts. They often glide and perch on wires or branches.
Swifts have extremely long, sickle-shaped wings and are among the fastest fliers, rarely perching. Not fully verified but they known to be even able to sleep and mate while in flight.

 Swallows have stronger feet and can walk or perch easily.
Swifts have very weak feet - their family name is Apodidae means "no feet". Swift normally cling vertically to surface like cliff and walls.

 Swallows build mud nests on structures like barns or bridges.
Swifts often nest in crevices,
Swifts are remarkable birds adapted for a life almost entirely in the air. They feed, drink, mate, and even sleep while flying, only landing to nest. Their streamlined bodies and rapid wingbeats make them exceptional aerial hunters of insects.

Swiftlets is another subgroup of swifts and they are known for their unique nests made of hardened saliva, found in caves across Southeast Asia. These nests are highly valued in Chinese cuisine and traditional medicine, leading to extensive farming in countries like Malaysia, Indonesia, and Thailand