what is sdp in sip code example

Example: sip sdp

INVITE sip:192.168.100.107:5061;transport=tls;User=phone SIP/2.0
FROM: <sip:+495251304613;[email protected];User=phone>;epid=6CDC4E66B4;tag=182da16c49
TO: <sip:[email protected];User=phone>;tag=1c789721132
CSEQ: 85419 INVITE
CALL-ID: 1f5219b6-2923-46de-8a19-8dd774e631ae
MAX-FORWARDS: 70
VIA: SIP/2.0/TLS 192.168.100.100:53951;branch=z9hG4bK2e7b2985
CONTACT: <sip:nawlync001.netatwork.de:5067;transport=Tls;ms-opaque=1984a8a7f0f3aaa4>
CONTENT-LENGTH: 373
SUPPORTED: 100rel User-AGENT: RTCC/5.0.0.0 MediationServer
CONTENT-TYPE: application/sdp

v=0
o=- 0 4 IN IP4 192.168.103.63
s=session
c=IN IP4 192.168.103.63
b=CT:99980
t=0 0
m=audio 6354 RTP/SAVP 0 13 101
c=IN IP4 192.168.103.63
a=rtcp:6355
a=crypto:2 AES_CM_128_HMAC_SHA1_80 inline:6kAMn8ieN/mPZNbxZTJjdkROJGc4GJzEYlkoHPhY|2^31|1:1
a=inactive
a=rtpmap:0 PCMU/8000
a=rtpmap:13 CN/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
a=ptime:20