In most states, thefts are classified (and charged) according to the dollar value of the property stolen. The lowest-level theft offense under a state’s penal code is commonly called petty (or petit) theft or larceny. The offense is usually defined as theft of property valued at or below a certain threshold -- that threshold can be anywhere from $50 to more than $1,000, depending on the state.
In some states, the lowest-level theft offense is not called “petty theft” or “petit theft”, but is referred to according to how the crime is classified (i.e., “Theft is a class A Misdemeanor if the value of the property stolen is less than $500.”).
Regardless of what it’s called, the lowest-level theft offense is always a misdemeanor (and may even be charged as a lesser crime such as an infraction, in some states).
With petty theft as the lowest rung on the ladder of theft crimes, other theft offenses will result in more serious charges as the dollar value of the stolen property increases. Usually, the most serious theft offense in terms of property dollar value -- theft of property valued at in excess of $20,000 for example -- is classified as a high-level felony ("grand theft") punishable by several years in prison and a fine in the tens of thousands of dollars.