In Bali and Indonesia you can expect the 2 pin socket and plug as used in larger parts of Europe. Whether you are staying in a hotel or in a private villa you should be able to get an adapter if you ask for one. The pins are round, not flat or rectangular.
Need an Adapter :
If you come from Australia, Japan, USA, Malaysia, UK, Canada, Singapore, and some countries in Africa you will most likely simply need a plug adapter otherwise the plugs for your electrical appliances will not fit into the "Bali Socket", although the voltage should be o.k.