The search warrant is a written piece of paper that gives law enforcement the ability to search you, your car, or your house. According to FindLaw, they can search for anything that might have the information that they want. The reason they need a warrant is because there is this whole concept of the right to privacy. The constitution protects you under the Fourth Amendment of being free from unreasonable search and seizure from the government.
The whole concept is because you want to assume that people have their rights to privacy, you are not going to give law enforcement the ability to breach that unless they have a good reason to do so. In a search warrant, every police officer is going to attach a probable cause affidavit. The information in that probable cause affidavit is going to have to be recent and specific enough to show what they think is wrong. It will have to be reasonably related to what information they want. So if the police have suspicion through maybe observations that they believe you might be involved in drug dealing, they are not going to be able to turn around and request something in their warrant or take something in their authorization that is not reasonably related to drug dealing.
The specificity of the actual written document that they have is significant because if they mess up anything on those documents, then the fruits of that search may be excludable at court. There are also exceptions to that warrant requirement. These are things that they can do things, and they can take without the necessity of that search warrant.