Chhand means meter - a type of construction of poetry in Sanskrit language; like Dohaa, Chaupaayee, Savaiyaa, Sorathaa, Kundaliyaan in Hindi poetry.

For example - Dohaa has four sections in two lines - first and third sections are of 13 Maatraa, while second and fourth are of 11 Maatraa, besides the last letter of second and fourth section should be short and match; while Sorathaa has opposite to this - 11 Maatraa should be in first and third sections, and 13 Maatraa in the second and fourth sections of those two lines, besides the last letter of first and third sections should be short and match.

Sonnet is in English poetry. It has 14 lines - three stanzas of 4 lines each plus 2 lines more. In the stanzas the second and fourth lines of a stanza should rhyme; while the last two lines should also rhyme.

There are seven types of Chhand in Sanskrit poetry - Gaayatree, Brihatee, Ushnik, Jagatee, Trishtup, Anushtup, and Pankti. Among them, for example, Gaayatree Chhand has 24 syllables in all (8+8+8 in three lines); Anushtup Chhand has four parts and has 32 letters in all (8+8+8+8). Chhand are used in writing Vedic literature.

Bhaagvat Puraan, 3/ref says that ---

Ushnik Chhand appeared from Brahmaa's fur (Rom);
Gaayatree Chhand appeared from his skin;
Trishtup Chhand appeared from his flesh;
Anushtup Chhand appeared from his nerves;
Jagatee Chhand appeared from his bones;
Pankti Chhand appeared from his Majjaa;
Brihatee Chhand appeared from his Praan (soul).