Im not really sure about what your first question is asking but here is a link explaining every part and its use.
http://lifehacker.com/5826509/how-to-build-a-computer-from-scratch-lesson-1-hardware-basics
And then here is what I would consider to be a fairly good PC build I left out a OS and monitor as well as other accessories.
PCPartPicker part list / Price breakdown by merchant
| Type | Item | Price |
|---|---|---|
| CPU | AMD FX-6300 3.5GHz 6-Core Processor | $97.88 @ OutletPC |
| CPU Cooler | Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler | $24.99 @ Micro Center |
| Motherboard | Gigabyte GA-990FXA-UD3 ATX AM3+ Motherboard | $149.75 @ OutletPC |
| Memory | G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1600 Memory | $49.85 @ OutletPC |
| Storage | Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive | $51.88 @ OutletPC |
| Video Card | MSI GeForce GTX 960 4GB Video Card | $214.99 @ Micro Center |
| Power Supply | Corsair CX 500W 80+ Bronze Certified Semi-Modular ATX Power Supply | $29.99 @ Newegg |
| Prices include shipping, taxes, rebates, and discounts | ||
| Total (before mail-in rebates) | $664.33 | |
| Mail-in rebates | -$45.00 | |
| Total | $619.33 | |
| Generated by PCPartPicker 2015-11-08 23:11 EST-0500 |
PM me if you have any other questions