A Remote Access VPN (Virtual Private Network) is a connection technology to provide secure and confidential connection of remote users to internal company resources through the Internet. The remote company user needs to have a VPN client software (e.g Cisco VPN client)  installed on his/her laptop plus a normal Internet connection (through Dial-up, broadband ADSL, wifi hotspot etc). Since traffic from the remote user will be passing through the untrusted Internet, it has to be encrypted to keep data confidential. To achieve confidentiality, the IPSEC protocol is used to encrypt and secure the user data.
Cisco VPN client is the most popular software used to provide remote access connectivity to the corporate home network. 

The figure above shows a basic setup for a remote employee using Cisco VPN client to connect securely over the Internet to his corporate network. First, the remote user connects to his public Internet Service Provider. Next, the user starts his Cisco VPN client installed on his laptop and initiates a VPN connection to the company VPN server. This can be a Cisco firewall (PIX or ASA), a Cisco VPN concentrator, or a Cisco Router with IPSEC software. Once the VPN connection has been established, the remote vpn user can communicate with internal company servers and resources just as if it were a local host.

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