The Pixel 3 Lite will apparently run on the Qualcomm Snapdragon 670, a new mid-range processor that's not likely as powerful as the Snapdragon 845 that's turning the wheels in the regular Pixel 3.
The Lite packs 4GB of RAM, which is fine for the mid-range category that the Pixel 3 Lite belongs to. It will, however, make the regular Pixel 3's 4GB of RAM look relatively meager.
As for storage, we can expect 32GB of flash memory, which is also on the low side. But as Andro News mentions, there's little need for much storage space if you use cloud services like Google Photos and media streaming services like Spotify for music.
The Pixel 3 Lite will also only have one loudspeaker found on the bottom of the phone, whereas the regular Pixel 3 has two front-facing loudspeakers.