Can someone tell me, how to send Sia via "siac" ?
"siac help" should tell you all you need to know.
siac is organized by subcommands. The wallet subcommand is "siac wallet". You can get help specifically with wallet commands with "siac help wallet".
Specifically, you can send money with "siac wallet send [amount] [address]". Note that the amount can be in exp. notation, e.g. 5e27. Also note that the amount is in base units, not SC or KS (5e27 = 5KS).
When everyone refers to Siafunds, what is that referring too? The amount of KS .... or more? confused.
Siafunds are assets that were sold in our crowdfund last year to fund initial development of Sia. They entitle the owner to receive a portion of all host income. i.e. they generate passive income. More info at
http://www.siacoin.com/sianotes.html