Can any tell me what is difference betwwen switchgear and paralleling switchgear ?

"Switchgear" is a generic term that refers to typically the main service entrance equipment, that is 1000 amps or larger. It will consist of the Main Disconnect Switch, overcurent protection, ground fault protection, and other accessories. It may also include the metering equipment, such as CT's (current transformers) and PT's (Potential transformers). This can also continue to include additioanl sections that handle distribution to smaller panelbaords etc.

Paralleling Switchgear will be to connect more than one power source to one load for either capacity or redunancy. For example, a hosital may have a 4000 amp utility service, but need more than one generator to provide a full 400 amp capacity.

To expand on TKRussell's answer Paralleling switchgear typically has logic built in which controls the power sources (typically generators) to adjust frequency and power output so that they can operate on the same bus and split the load based on the intended design.