A proxy and a VPN is quite similar in functionality but there are definitely some differences.
In short, a VPN establishes an active connection/tunnel between your device and the VPN server, and the traffic meant for that VPN server will go through the tunnel and get forwarded to your destination. A proxy is not an active connection, it's essentially just receiving requests as they come and forwarding them to your destination. In terms of the connection, think of a VPN like a phone call where you dial a number and an active connection gets established, while a proxy is more like text messaging where you simply send off messages and they go to the destination.
Here is a longer answer for those that are interested.
A VPN is a Virtual Private Network. They were created for that specific purpose, to create a private network that can be accessed remotely. Think of it like your home network. All the devices are connected to the same router and can communicate with each other using this router, without ever having to connect to the outside internet. A virtual private network is the same thing, but the network is on the internet so devices from all over the world can access it. When this technology first came out, it was used mainly for office and remote work networks so that people can access internal company resources remotely using the company VPN but not have those resources connected to the open internet directly.
Nowadays the definition of a VPN has changed quite a lot. The original function of a VPN still definitely exists and lots of company use them for internal resources, but most people are more familiar with the consumer VPN services that exist such as Windscribe. It's a tool to mask your IP and internet activity, provide anonymity, make you appear as though you are in other countries, etc. The underlying technology is still the same, but the functionality has been altered to provide end-users with many benefits.
A VPN works by establishing an active tunnel between your device and the VPN server. All the traffic that is meant to go through that tunnel is then sent to the VPN server, and the server will handle the request accordingly. If you are using an internal company VPN, internal domains like resources.company.dev will give you an error when visiting unless you are connected to the VPN, and if you are then you will be able to access the resources present on that domain. If you are using a modern consumer VPN like Windscribe, then all your traffic will be funneled into that tunnel (unless you exclude it) and the VPN server will forward it to the destination using the VPN server IP instead of your own.
A proxy, on the other hand, is a bit simpler than a VPN. It's a server that will basically just forward your request to whatever destination. You send a proxy a request, the proxy server sees that request and forwards it to the site domain/IP you are trying to visit. Proxies can have authentication as well so some companies will use an authenticated proxy for internal resources but there are fewer things possible using a proxy for this, instead of a full virtual private network.
In terms of Windscribe, we use both proxies and VPNs, depending on the client you're using. Proxies are used if you are connected to Windscribe in our browser extension while a VPN tunnel is established when using out desktop app or mobile apps or if you use a custom config such as on your router.
One more detail to mention, WireGuard is a more modern VPN protocol that we have implemented into our apps but it functions slightly differently than the older OpenVPN and IKEv2 protocols. WireGuard will not establish an active VPN tunnel, it will actually function more like a VPN-proxy hybrid. You point your device to the VPN server and WireGuard will send your traffic that way whenever your device sends it. The only active connection between your device and the VPN server is a periodic handshake that verifies the connection to the server is still there. And even though the WireGuard connection isn't an active tunnel but more like a proxy, it will still offer all the functionalities of a virtual private network, so you get the best of both worlds.