Microphone PCB Questions
This circuit is basically a really simple JFET amplifiers with supply filter and a pot for adjustable attenuation, similar to this. 
  

The JFET is a voltage controlled voltage source which can offers a high impedance input like 1M and lowers the output impedance but is still considered high impedance as it is must a single transistor pre-amp with a voltage gain of less than 10 and an attenuator pot. That's a guestimate based on the very primitive description.

scam alert

From looking at the website, I don't have anything good to say about them and their price gouging and unprofessional content is alarming.  What they offer is worth at best $10 in parts for a sale price of $168.02 is unethical IMHO.

If you did not get a schematic with the kit, I feel sorry for you and shame to anyone who advised you to get this DIY kit.  They also have linear circuit DIY kits for $269 . (obvious scam)

e.g. they mention here a pre-biased  NOS FET, which sounds amazing as this is a fake identification that does not exist, except on other sites that reference the same parts NOS FET meaning "New Old Stock".

The circuit will most likely contain a "JFET biased pre-amp" of dubious quality.

My only advice if you have one is to ensure when soldering the parts, that solder flows thru the plated thru holes incase they are bad. This only takes 3-5 seconds with a clean iron tip while applying solder. No more than 5 seconds.

Then avoid this site as it is a scam DIY kit site. Amazon and Ebay have much better completed boards for 10% of this cost.

P.s.

If you are really anxious to try simple DIY kits , consider something like this. http://talkingelectronics.com/projects/200TrCcts/200TrCcts.html#34  but keep in mind this is like 20~40 yr old technology... but at least it is only a kit of 15au$ from which you can make upto a dozen different simple circuits.