A scale is, essentially, a series of musical notes. That's the very, very basic thing you need to understand.
In our normal tonal music like classical or rock, scales are important because we derive harmony from the way the different notes in a scale relate to each other.
Let's start with the C Major scale. It's easier this way because of the piano keys and it's probably the most basic scale.
The C Major scale has 8 notes and it's called a diatonic scale(you'll understand more as you progress). The notes of the C Major scale are all the white keys on a piano keyboard and they are: C D E F G A B C.
These 8(or 7 if you do not count the "high" C) notes form a scale and these notes, when played together in succession, sounds alright to your ears. You'd have just learned the first thing about harmony.
On a guitar, you'd realize it's not that easy to find the notes of the C Major scale because the strings look different from the keys of a piano. But no worries.
If your guitar is tuned in Standard E(EADGBe), you'll find that the C note on the 1st string is on the 8th fret. That forms your first C of a scale.
The second note, the D, will be on the 10th fret, well because the 9th fret is the note C# and it doesn't belong to the scale of C Major.
Knowing these simple knowledge like which notes are not in a particular scale will give you an idea of what an interval means, which is the "distance" between two consecutive notes in a key.
Since C to D requires the note C to travel from C to C# to D, we call that one interval or a whole step in guitar speak.
D to E will also be one interval but then E to F is half an interval as E# is actually a F.
Once you realize this important thing, you will realize that the intervals between music notes are constant in a particular kind of scales.
For example, we also have the E Major scale, the A Major, etc and you'd realize that the 3rd note of that scale will always travel half an interval to the 4th note of the scale.
So, back to the C Major scale with the two notes C and D on the 8th and 10th fret of the first string of your guitar respectively.
The E note will be on the 12th, the F will be on the 13th, the G on the 14th and it goes on. But that's only on a string.
So, you will need to figure out the different notes on different frets on different strings.
You will then find there's a pattern to a scale across the fretboard on different strings and that will be roughly what the guides on the Internet are trying to tell you.
That's all from me and hope it helps.