Hi.
If you mean pronunciation of a letter 's' at the end of words, it is more or less as follows:
1) 's' is pronounced as /s/ when follows voiceless consonants; e.g. ca
ts ('t' is a voiceless consonant) --> /kæts/
2) 's' is pronounced as /z/ when follows voiced consonants; e.g. do
gs ('d' is a voiced consonant) --> /dɒgz/
3) 's' is pronounced as /ɪz/ when follows 'hissing' sounds /s,z,ʃ,ʒ,ʧ,ʤ/; e.g. jui
ces, cau
ses, aboli
shes, camoufla
ges, wa
tches, bri
dges --> /'ʤu:siz/, /'kɔ:ziz/, /ə'bɒliʃiz/, /'kæm.ə.fla:ʒiz/, /'wɒʧiz/, /briʤiz/
I hope it helps.
Seba
PS
See also:
https://www.usingenglish.com/forum/pronunciation-phonetics/57203-s-s-z.html