These schemes are also called company pension schemes. It's a scheme set up by an employer to provide pension or death benefits for its employees. An occupational pension can provide pension benefits on a money purchase, defined benefits, cash balance or hybrid arrangement basis. The two most common arrangements for occupational schemes are defined benefits (such as the LGPS) and money purchase
If you leave a job you'll normally have to stop building up pension savings in that employer's scheme. These benefits can be transferred to your pension in the LGPS. Any transfer into the LGPS would buy extra pension which is then added to your pension account, unless the transfer is from a public service pension scheme and is transferred under the Club transfer rules in which case any part of the transfer that relates to final salary benefits in that scheme (usually membership up to 31 March 2015) would buy pre 1 April 2014 membership in the final salary scheme.