What the these terms mean?

when i read some document i meet a lot of telephony terms. i can not understand .help me!

  1. out of band
    2, inbound and outbound, what the difference between inbound and ingoing?

This refers to DTMF (i.e., dial tones). With SIP, it is possible to send these as part of the audio stream (inband) it is also possible to send them separately from the audio stream (out of band). SIP can be configured to do either. If the other end supports it, out of band is generally better i think.

Inbound is coming in to your system, outbound is going out from your system. There is no difference between the terms inbound and ingoing - although “ingoing” isn’t really correct, it should be incoming (and outgoing).

ok.i see .thank you