LinkObject["name",n] is an object that represents an active MathLink connection for functions such as LinkRead and LinkWrite.
LinkConnect, LinkCreate, LinkLaunch and Install all return LinkObject objects.
The integer n is a serial number used to distinguish links with the same name.
name is typically the name of an external program, or an internet TCP specification of the form port@host.
See the Mathematica book: Section 2.12.2, Section 2.12.9.
See also: Links, LinkReadyQ, InputStream.
See the Further Examples for LinkLaunch.