These seem to be a very common style of component on Aliexpress and sometimes on eBay too. It's a spark ignitor for gas that could be used for cooker, ovens or other applications. Unlike oil igniters or larger scale gas units, it doesn't have a continuous hot spark, but just pulses low current sparks continuously until the gas/air ratio hits the sweet spot and ignition occurs. The design is gloriously simple due to the use of a specialist component designed almost exclusively for generating high current pulses used to drive the transformer assembly. The format of these varies. This one appears to have three separate high voltage secondaries, which raises the intriguing possibility of wiring them in series for a single higher voltage spark. Other versions have a common ground connection and several outputs referenced to that. If desired, the PCB could be removed for driving your own custom transformer or pulse coil. Or alternatively you could take inspiration from its design for your own PCB design. It's a classic circuit. The very high value resistor is a discharge resistor designed to gently discharge the main capacitor to prevent a rogue unexpected spark due to retained charge, or possibly to avoid false triggering due to leakage current on the supply circuit causing the capacitor to gradually charge up until a spark occurs unexpectedly. Supporting the channel with a dollar or two on Patreon helps keep it independent of YouTube's quirks, avoids intrusive mid-video adverts, gives early access, bonus footage and regular quiet Patreon live streams. https://www.patreon.com/bigclive #ElectronicsCreators