Every scale this site shows you has seven notes. Five of them are always safe; two of them are opinionated. The pentatonic trick is simply this: remove the opinionated ones.
In a major scale, drop the 4th and the 7th degree. In C major that means dropping F and B. What remains, C D E G A, is the major pentatonic: five notes with no half-step friction against any chord of the key. There is nothing left that can clash, which is why beginners sound instantly better inside it.
The 4th and the 7th are the two notes that sit a half step away from chord tones. They are wonderful notes, but they demand resolution: play them and your ear expects you to move somewhere. Remove them and every note you play is already home. That is the whole magic, no talent required.
The riff of "My Girl", the melody of "Amazing Grace", most guitar solos you have ever air-played: pentatonic. Entire genres, from blues to country to rock, lean on these five notes.
Try it here: find your key on the detector, look at the seven scale chips, and simply skip the 4th and the 7th while improvising. Ten seconds of theory, a lifetime of safe solos.