Download means getting information from another computer or server. The opposite of downloading is uploading, which is sending data to another computer. Usually we do not say "download" for a single web page (for example when you open this page on your computer). When we say we downloaded something, it is normally a bigger computer file, like data or a computer program.
The word downloadable means the ability to get information or data from an owner for one's use. The source is expected to be authentic and have the right to send it. At the user's end, the downloaded information or data are to be used based on agreement notice.
In the 21st century, it is very easy to download files or informations - legally or not - from the internet.
As most non-technical users use the word download to talk about any data transfer, the word "sideload" is sometimes used for local to local transfers as distinct from distant ones.