A generalization of this is fundamental strings which are 1-dimensional objects . However their stringy nature has important implications as we will see.
Strings can be open or closed .
As they move through spacetime they sweep out an imaginary surface called a worldsheet . These strings have certain vibrational modes which can be characterized by various quantum numbers such as mass, spin, etc. The basic idea is that each mode carries a set of quantum numbers that correspond to a distinct type of fundamental particle. This is one of the most attractive features of string theory. It naturally and inevitably includes gravity as one of the fundamental interactions.