Electronics

Development Resources

Really some of the best resources:

Analog.com Tutorials

TI Training and Videos

More

SparkFun Learn

Adafruit Learn

Hackaday

Way more to add.

Specifics

What are Microcontrollers?

What are Integrated Circuits?

PCB Basics

Analog-to-Digital Converters

What are Biopotentials

For every chip you are interested in, read the datasheets thoroughly. They are INVALUABLE resources for learning analog circuit design.

Go to Youtube, type in any concept you want to know

Specific youtubers to check out:

Phil's Lab

Robert Cox

ElectroBOOM

Physics Videos by Eugene Khutoryansky

Gadgetronics

Zack Freedman

3Blue1Brown