If you are more advanced in a Technology than an ally you can send them enough information to unlock a new level.
When you share technology to another player you will not lose anything yourself. The other player simply knows how to build the technology themselves.
A small fee must be paid when giving tech to another player. The higher level the technology, the greater the fee.
You can also send money to an ally to help build their empire or in exchange for technologies.Note: When selling technology to another player there are no game mechanics that will ensure you get what you pay for. You must trust that your ally will send the money or technology as promised.