Theft refers to the unauthorized taking of property. Obviously, this is just a broad definition. It is very difficult to understand possible consequences without knowing several details of your theft charges.
To start, you have to look in the right jurisdiction. In California, theft is a statutory offense with a large amount of case law for specific situations. There are various levels of punishment with two decisive factors: the property and your previous criminal record.
As explained on FindLaw, California law sets fines and imprisonment for theft. Petty theft is for property with a value of up to $950. Your conviction could lead to a maximum fine of $1,000, six months imprisonment or both.
For property with a value of less than $50, you could be guilty of an infraction. This would be punishable by a fine of up to $250.
If you have a prior conviction, you might have a misdemeanor charge. Your conviction could result in up to one year in jail. Alternatively, the state might pursue felony theft charges against you. The penalty for this could be up to 16 months, 2 years or 3 years imprisonment.
If you plead guilty or receive a conviction for stealing over $950 worth of property, this would be grand theft. It has similar penalties to misdemeanor and felony petty theft: up to one year imprisonment for a misdemeanor; up to 16 months, two years or three years for a felony.
There are other things you might want to consider, too. For example, charges involving stolen firearms could result in more severe penalties. If you face charges for theft of property that are unlawful for you to possess, such as prescription medication, you might also face charges that relate to that property.