An ADSL wireless access point/router will allow the two machines to talk to each other.
You ask if they will "split" the Internet connection. For the most part they will share the connection's pipeline pretty much transparently, ie they will
independently access the internet with a user on each machine able to do his/her own thing without interfering with the other until the total of their demands exceeds the bandwidth you've paid for. At that point the sharing of the pipeline becomes evident.
That is, the pipe to your place is only so big. If a person on one computer wants to do something that uses all the available capacity of the pipe, such as download a big file, and then another person on the other computer wants to do the same thing, then each will run at half speed. But with two people simply surfing, each will hardly be aware of the other's presence because surfing generally doesn't "suck much out of the pipe".
Re emails - with Windows basic email such as Outlook Express, generally the email stays with the computer that collects it.
Having said that, most email clients, including OE, allow you to choose to leave the email on your ISP's server (that is not the default - you have to choose to do it). This allows you to go back with another computer and download it again, thus giving you a copy of the email on both computers.
Also, different email clients allow backup, import and export of emails in different ways, so you can transfer emails between machines, the method depending on the client you use.
If you're using Outlook Express, check
here
AA