Classifier is a pronoun-like linguistic symbol that represents a class or group of referents. In ASL, a noun should be signed first before using its classifier to refer to it until a subject or noun is changed.
Learn how locative classifier is used in American Sign Language.
The signer begins with the ASL word table [left image] and then assigns it a pronominal classifier (palm faced down) for the table (in the same way that you speak "Ms. Jane Doe is..." and then "she... she..." through the sentences). This classifier can be used to refer to a table, desk surface, etc.
The signer then utters the ASL word cat (the noun) and immediately assigns it the pronominal classifier [below]. Notice that the signer still holds the pronominal classifier for the table.
"The cat is sitting below the table." The bent 2-handshape, that is the classifier, represents the sitting cat.
Or, "... sitting on the table".
Or, "... lying down on the table". The signer has changed the palm orientation of the classifier. If she lowers her eyelids at the same time she signs "lying down", it means the "it (the cat) is sleeping on the table."
Locative CL can be used to show the pathline of something. The pathline classifier in sign language, particularly ASL, uses a movement to express a motion of the subject or object. Index finger is the common classifier handshape for the pathline in a verb predicate.
Gloss: ball/\ thrown cl-pathline[medium]
The LCL-pathline can be used for the movement or trace of a bird flying across the sky, a horse running around the track, a ball flying high, etc.
Sometimes LCL-pathline is used instead of a semantic or a decsriptive classifier that might be awkward to use. For example, in this sentence "BIRD/\ IX1 FLY CL:1-pathline-around-in-sky", the semantic classifier handshape ILY is not the right classifier for BIRD. It's used for an airplane.
Another example, HORSE/\ IX1 GALLOP CL:1-pathline-around.
Using the pathline classifier, you can adjust the movement to describe a degree of intensity, speed, or motion of something.
If you're not sure how to use classifiers properly, observe Deaf-native signers.
Also see what is classifier? for an introduction.