How do we use the subjunctive?

The subjunctive is a mood that is mostly used for expressing doubt, hope and talking about something that is not definite. It is based around a subjective idea rather than an objective one; meaning that it is not concrete.E.g. La mela è rossa- The apple is red (objective) is concrete and factual ...whilst...Penso che la mela sia rossa- I think the apple might be red (subjective) is based on the idea of possibility or uncertainty.Notice how in Italian, the subjunctive mood is very often linked with another verb with a conjunction such as 'che'. The example above is structured with the verb Pensare (to think) in the first person present tense + che +....+ essere (which in the subjunctive mood is sia)