E-Liquid (or e-juice)

.. is flavoured liquid nicotine which you use to refill a cartomiser, cartridge, or tank. 

E-Liquid is kinda like the 'roll-up' version of smoking.  If you don't mind a bit of work, and want a cheaper option, e-liquid is for you.  If you're a 'tailor-made' smoker and just want to 'plug-and-play', you might be better off with pre-filled 'cartomisers', where the nicotine is already in the product - you just screw it into the battery and off you go.  When the cartomiser runs out of nicotine, just throw it away.  The cartomiser option is more expensive, but both cartomisers and e-liquid options are much cheaper than cigarettes.

Recommendation:   If you like a ritual and don't mind the 'fag' of it, and want to save a bit of cash, give e-liquid a go, but I think pre-filled cartomisers are better for 'newbies' - you can always switch to liquid later.  You usually get a wider choice of flavours with e-liquid. Smokers of 'tailor-made' cigarettes will probably use cartomisers, at least to start with.  Whilst tobacco and menthol flavours are favoured by newbies, vanilla is an excellent alternative and is a firm favourite with extablished vapers.