Brane

1-dimensional strings, as well as 0-dimensional point particles and 2-dimensional membranes may be generalized to a higher dimensional object. These objects are called branes and they are dynamical objects that propagate through spacetime according to the rules of quantum mechanics. Branes can have mass and even charge. The term originated in 1987 as a contraction of "membrane." 

To explain, a point particle is a 0-brane, a string is a 1-brane, a membrane is a 2-brane. A corresponding object of dimension "p" will be called a "p-brane." Michael Duff and others coined this term in 1988. The p-brane sweeps out a p+1 dimensional volume in spacetime. This is called its world volume. 

An important class of branes that arises when one considers open strings are D-branes. As an open string propagates through spacetime, its end points are required to lie on a D-brane. The brane satisfies a certain class of boundary conditions known as "Dirichlet conditions," from which comes the 'D' in D-brane. 

In string theory and supergravity, branes are physical objects, that essentially generalize the notion of a point particle to higher dimensions. Branes are dynamical objects. They can propagate through space according to the rules of quantum mechanics. Branes have mass and can have properties such as charge. 

I now want to discuss the distinction between p-branes and D-branes. 

p-branes

In zero dimensions, we have a point particle. In 1 dimension, we have a string. In 2 dimensions, we have a membrane. Indeed, you can consider higher dimensional branes. A p-dimensional brane is normally called a p-brane. The term "p-brane" was introduced by Michael Duff and others in 1988. The "brane" comes from "membrane." "Membrane" refers to a 2-dimensional brane. p-branes sweep out a (p+1)-dimensional volume in spacetime known as its worldvolume. 

The dynamics of a D-brane world volume is described by a gauge theory. Gauge theories are highly symmetric physical theories. They are also used to describe the behavior of subatomic particles in the Standard Model of particle physics. This relationship has led to insights in gauge theory and quantum field theory. An example of this is the AdS/CFT correspondence, where difficult problems in gauge theory are translated into easier calculations in string theory.