Cigarillos or small cigars are those cigars smaller than your average petit corona in length and generally with a thinner ring gauge than the thinnest panatelas. Its a bit unusual to find hand made cigarillos; most are machine-made due to the extensive use of short filler tobacco (tobacco from shredded strips of whole leaves). It is usually more cost effective, efficient and easier to use machines in the making of these cigars.
The results: small cigars, normally slightly larger than your average cigarette, that are relatively cheap and often very representative in taste of their full sized cousins. The only downside is, due to the use of short filler tobacco, smoking a small cigar tends to leave small fragments of tobacco in your mouth after each draw, especially towards the end of the cigar.
An excellent small cigar is the Cohiba Club (normally packaged in small packs of 20 cigars that can fit into your top shirt pocket) and the wonderfully tasteful Avo Domaine Puritos (normally packaged in 10s in a small tin case).