Step 1: Read the question.
We must find an essential part of the offence of theft as defined in Section 378 of the Indian Penal Code, 1860.
Step 2: Recall the meaning of theft.
Theft means dishonestly moving movable property out of the possession of a person without that person's consent.
Step 3: List the key ingredients.
There must be movable property, the property must be in someone's possession, the accused must move it, the moving must be dishonest, and it must be without consent.
Step 4: Test Option 1.
Option 1 says moving movable property out of a person's possession without consent. This matches the definition exactly. So it is a correct ingredient.
Step 5: Test the other options.
Option 2 is wrong because theft can happen anywhere, not only in a public place. Option 3 is wrong because using force is part of robbery, not plain theft. Option 4 is wrong because immovable property like land cannot normally be stolen.
Step 6: Final answer.
Even a small movement of the property with a dishonest mind completes theft.
\[ \boxed{\text{The movement of movable property out of a person's possession without their consent}} \]