How shall I understand the output of `dig`?

Does `dig` return the resource records in the database of some DNS server? If yes, which DNS server's resource records does `dig` return?

For example, `dig` doesn't seem to return the resource records of DNS server `a.edu-servers.net`. 

 $ dig @a.edu-servers.net robot.cs.washington.edu
 
 ; <<>> DiG 9.11.3-1ubuntu1.3-Ubuntu <<>> @a.edu-servers.net robot.cs.washington.edu
 ; (2 servers found)
 ;; global options: +cmd
 ;; Got answer:
 ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 2401
 ;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 3, ADDITIONAL: 7
 ;; WARNING: recursion requested but not available
 
 ;; OPT PSEUDOSECTION:
 ; EDNS: version: 0, flags:; udp: 4096
 ;; QUESTION SECTION:
 ;robot.cs.washington.edu.	IN	A
 
 ;; AUTHORITY SECTION:
 washington.edu.		172800	IN	NS	marge.cac.washington.edu.
 washington.edu.		172800	IN	NS	hanna.cac.washington.edu.
 washington.edu.		172800	IN	NS	holly.s.uw.edu.
 
 ;; ADDITIONAL SECTION:
 marge.cac.washington.edu. 172800 IN	A	140.142.5.13
 marge.cac.washington.edu. 172800 IN	AAAA	2607:4000:200:43::13
 hanna.cac.washington.edu. 172800 IN	A	140.142.5.5
 hanna.cac.washington.edu. 172800 IN	AAAA	2607:4000:200:42::5
 holly.s.uw.edu.		172800	IN	A	173.250.227.69
 holly.s.uw.edu.		172800	IN	AAAA	2607:4000:301:1::69
 
 ;; Query time: 46 msec
 ;; SERVER: 192.5.6.30#53(192.5.6.30)
 ;; WHEN: Mon Feb 11 16:27:09 EST 2019
 ;; MSG SIZE rcvd: 253