Hi @pasquaj
Yes all those specifications are a nightmare to think about as your experiance grows.
I will try and help several of these terms can apply to timber at the same time so just look at them one at a time.
Generally most of the wood you buy will be pre seasoned or kiln dried at hardware stores that means the moisture level in raw wood is reduced and the wood will shrink by around 10% this also reduces the chance of timber warping. Vs buying direct from a logging yard you might get unseasoned and if you built a deck with that straight away the floor will shrink by 10% and cracks will appear,
F(5-17) as you mentioned refers to its structural grade eg 5 is weaker than 12 etc. F17 is used in the higher stress applications and is usually price accordingly. But for use DIYers most timbers will suit our needs At Bunnings some timber will be rated as structural so that will be stronger than Non Structural. It would be rare for DIYers to need to use structural wood but is optional/
MGP10 Stands for Machine Grade Pine a rating making it strong and durable. Versatile use indoors, Lightweight, flexible nature,
Another term is DAR or just " Dressed " all round this means the timber id generally cleaner straighter has less knots (Weak points and blemishes) and most of all has machined clean edges to a specific size. We pa.y more for this and would be mostly used where exposed timber is desired.
As you already know as you said H3 is treated pine for outdoors for pine off the ground and is wet occasionally
H4 is treated pine in the ground with some wet feet ie posts etc
H5 is treated pine for wet ground applications typically H5 is not common at hardware stores more H3 H4
So If your project out doors best to use Treated pine. H3 to H5 from dry to wet conditions.
All timber can be used indoors . Stronger look for Higher F rating, smoother flatter look for dressed etc.
You can also paint a lesser timber etc to improve its weather resistance indoor timber can come outdoors etc.
