10Base2 is a co-axial bus-based physical cabling for Ethernet. In the OSI seven layer model, this is LAYER 1 - PHYSICAL.
10base2 follows the following naming structure: Speed in Megabits/second, followed by the term 'base', to signify baseband transmission, and some other qualifier dependant upon the technology. In this case, the 2 refers to the maximum distance allowed in this protocol - about 200 Metres (185 or so, in fact). 10base5 is the only other similar technology which uses the same nomenclature - and it allows up to about 500 Metres.
Other names for 10Base2 include thin net, cheapernet, curtainwire and coax.
There are two general styles for 10Base2 cabling. The common style involves the use of one tee connector per station, with coaxial cable joining to each station in series. At the end of each bus there is a 50 ohm connector across the core/shield which is commonly referred to as a TERMINATOR. Because this is a bus system, any fault in the wire will affect all stations.
The other variant of 10base2 is made by AMP and offers the ability to add and remove a station without interfering with the rest of the bus. This method uses a short (under 1 metre) flylead with an unnamed push-in connector to a wall plate, essentially taking the place of a tee connector.
Regardless, 10base2 uses BNC connectors almost exclusively for connecting to stations, terminators and other equipment.
10base2 can be used on the same network as 10BaseT or 100BaseT. Because 10base2 is at the physical layer, a hub or media converter is required to change the layer two (logical) to a new layer one (physical) Hence one may have a hub with 100BaseT to your flash new machines, and a 10Base2 segment for older items like an Xterminal.
10base2 is not recommended for use nowdays - 10BaseT/100BaseT hubs are cheap and UnshieldedTwistedPair (AKA UTP) cable is not expensive either. However 10Base2 is very cheap (read that as "don't expect to pay anything for cable cos most places are throwing it out")
A 10Base2 segment is limited to a total length of 185 metres from terminator to terminator. You can have up to 100 stations with a minimum of 1 metre between stations, however the performance will degrade with additional stations.