Hi
sh ip arp is the table where all IPs are stored and where they are resolved from MAC to ARP l2 to l3 , they may not be directly connected though as this is held on the L3 switch and can show ips from devices connected to layer 2 switches it has resolved in its own switch , the layer 2 switch if pure l2 will not have the full arp table
CDP is directly attached Cisco devices a discovery feature , it only sees Cisco and some other vendors devices which allow it but it wont see all connected devices like a HP pc or some 3rd party printer etc , LLDP can see most of those though as its open standard
