What are trunk and access in vlans and why we use access and trunk in vlan?

Trunk ports are used for connectivity between switches whereas access ports are used to connect the devices such as computers, printers and other devices. One cannot extend the data from one switch to another switch access ports through trunk port. It can only be extended through the access port of the switch.

A port on a switch is either an access port or a trunk port.

Trunk port is used to connect between switches and access port is used to connect to computers lap top printers etc,

A trunk port can have two or more VLANs configured on the interface; it can carry traffic for several VLANs simultaneously

An access port can have only one VLAN configured on the interface; it can carry traffic for only one VLAN.

I hope now you understand the differences.

This questions remembers my knowledge back. 

Thanks

You can assume it as a tunnel via this you can communicate on VLAN devices. You can send/receive your files & data through this port. It uses ISL.

more https://www.techopedia.com/definition/27008/trunk-port