Seeding is a process of sharing chunks of files that have been downloaded 100% with other users on the BitTorrent network.
By ticking the 'Seed Finished Torrents' you allow other users on the BitTorrent network to download chunks of files you downloaded from the BitTorrent network yourself.
By ticking the 'Seed only on Wi-Fil' box, you allow other users on the BitTorrent network to download chunks of files you downloaded from the BitTorrent network yourself, but only if your device is connected to a Wi-Fi network. This option will allow you to avoid extra data charges from your mobile carrier.
If you don't tick any of the above options, you will not be seeding any files you've downloaded from the BitTorrent network.
Remember it is always a good practice to seed (allow for upload) at least the same amount of data you've downloaded. Seeding makes the content available to on the BitTorrent network and speeds up the download rates for other users across the network.
You should also know that any BitTorrent Client, including FrostWire, can seed the chunks of files DURING the download itself regardless of settings - it is a function built into the BitTorrent protocol. Although it is possible, it is very unlikely on an Android device, as it is weaker than most desktop computers, which will be prioritized for upload before a mobile device.