The main difference between the STEM toy and STEMbot is the coding to control element. Many toy claims the STEM toy credit and involves kids in building and designing, and even perhaps with simple motor actions, (like the original lego), but not until they have a way of control through coding then entered the realm of STEMbot.
And there are quite a bit of collection for the coding language as well. Scratch, Blockly, Arduino, Raspberry Pi are all popular choices for kids to learn coding at early age.
I would name a few STEMbots here worthy of review (and if any manufacturers out there disagree, please submit your entries in the Mfg Section!! Thank you.): Thymio, mbot, jimu, sphero. I’m sure you have your favorites so please comment as well.