Certain consonant clusters have special sounds in Italian. Their pronunciation changes when they come together and form one syllable (monosyllabic clusters).
CE, CI, CIA, CIE, CIO, CIU While ca, co and cu are pronounced as in English, ce and ci have a soft sound (palatal pronunciation), like in English che and chi.
GE, GI, GIA, GIE, GIO, GIU: The clusters ga, go and gu are pronounced like in English, but ge and gi have a "soft" sound (palatal pronunciation), like English je and jy (or jih).
GLIA, GLIE, GLIO, GLIU: When gl is followed by vowel i, it has the same sound as ll in Spanish words like caballo, lluvia, etc.
This exact sound does not exist in English, although a rather similar one is obtained pronouncing the sentence "I will call you", in which a double l is followed by y + another vowel.
The Italian sound is obtained by pressing the point of the tongue against the back of the teeth and flattening it against the hard palate.
When gli is followed by vowels a, e, o and u, the sound of i is lost; glia sounds like Spanish lla (close enough to English llya, but y should not be heard much), glie as Spanish lle, glio as Spanish llo, and gliu as Spanish llu.
Instead, when gl (without an i) is followed by vowels a, e, o and u, it is simply pronounced as in English, in words like glass, glove, glue.
SC, SCA, SCO, SCU, SCE, SCI, SCIA, SCIE, SCIO, SCIU: The cluster sc only has a special sound when followed by vowels e and i, in which case it sounds like an English sh in sharp, shelf, cash, shop.
In any other case (sca, sco, scu) the pronunciation is like the English one in scar scorpion, scub, scootera.