You go on about buying parts by copy-pasting the name into google and shopping at online vendors. Ebay works too, and indeed many shops have Ebay presence. Compare prices from a few different sources before buying. Keep in mind shipping costs.
If you don't know which component is better, type its name into google with 'benchmark' and look for a grade it gets. Compare with the grade of a different component of the same type on the same site.
It matters less what's inside (unless you're a min-maxing tech-whizz), more what grade is higher and if the difference is large enough to justify the extra cost.
There are also 'buying guides' of various levels of accessibility available online.
CPU: Intel CPU Core i7 3770 3.4 GHz / AMD CPU FX-8350 4 GHz
There are two processor manufacturers on the market: AMD and Intel. Intel makes more efficient processors, AMD makes them cheaper. As a result, you'll see AMD CPUs with higher clocking frequency that are cheaper and slower than Intel processors with lower frequencies listed.
The i7 and the next four numbers denote generation and model respectively. Generally the higher the number the more powerful a model.
With AMD, FX is the series name, the 8 indicates the number of cores and the rest in the model number - the higher the faster.
The number before GHz is the clocking frequency - how many cycles can a processor (core) perform per second. Simply speaking, how fast it is. These numbers are only useful for comparison between processors of a single manufacturer.
The two processors are comparable in performance. The Intel one is a bit faster, but AMD is cheaper. You're unlikely to see any difference in practice, unless you care for extra couple of fps in games.
The i7 is more energy-efficient.
It's important to get a motherboard with matching sockets though. 'AM3+' for AMD and 'Socket B' (aka 'LGA 1366') for the i7. These will be listed among the motherboard specifications.
i7 is a four-core processor with multithreading, the other one is eight-core. Does it matter what these do? I don't think so. It's got to do with many processes running in parallel, but they've become something of a standard recently.
System RAM: 8GB
This is the memory. It indicates how much data can a computer store and process without having to resort to moving stuff to and from hard drive. The more the better, 8 GB is a lot.
When buying, pay attention to whether it's DDR3 or DDR4 - the latter one is faster, but being recently released will be more expensive. AND you'll need a motherboard that can support it. Which type of memory can fit into a motherboard will be listed among its specifications.
If you'll see some numbers after DDR3/4, these indicate clocking speed - higher means faster. Faster is better.
Memory is generally the easiest to expand. You can have as much as your motherboard supports.
Graphics Card: Nvidia GPU GeForce GTX 770 / AMD GPU Radeon R9 290
Again, like with CPUs, two main manufacturers of graphics cards on the market: Nvidia (brand name: 'GeForce') and AMD ('Radeon'). No appreciable differences between the two.
The GTX 770 is slower but quieter, a bit less power-hungry and cheaper than R9 290. That's all there is to it. You'll get no more than about 5 extra fps in high-end games from the R9 290 over GTX 770.
Hard Drive Space: 40GB
I'm sure you know what HD is. The low capacity indicates it's an SDD - a solid state drive. It's a bit like an oversized RAM - it's got no moving parts, runs silently, is resistant to shock, writing and reading from it is very fast.
On the other hand, you can easily get a 1 TB (25 times more capacity) drive of the regular variety at a comparable price.
A sensible thing to do is to buy both - to install your system and maybe games on the SDD and use the regular HDD for long-term storage.
Also, 40 GB is low even for an SSD - there do exist up to 1 TB drives, just as there exit 6 TB regular HDD.
The rule of thumb is that you'll pay 6-7 times more for the same storage if you buy an SDD.
By the way, I don't believe you'll ever need more than maybe 250 GB of total storage unless you'll start hoarding videos and will never uninstall old games, but I know people like to get at least a terabyte because 'you never know'.
You'll need to get a power source unit (PSU) that can supply enough energy - 500W should be enough. If unsure, count how much Watts each component consumes - you need a bit more than the total.
And remember to match a motherboard to the processor socket, and memory chips to the motherboard.