First, strings names and numbers. We've shown the string names as standard tuning [E-A-D-G-B-E]. Our guitars can be tuned to thousands of different tunings. Standard is a baseline starting point for guitar.
Tablature [download blank] is a system of notation which utilizes 6 horizontal lines to indicate strings, & numbers on the lines to show which frets are to be played. Horizontal lines = strings. Numbers on the lines = frets. Every verticality (column) is a moment in time, just as with music notation. If a number appears alone, this means to play that tone alone. When numbers are stacked on top of each other, this means you will play those tones at the same time, as in a strummed chords.
Guitar tab is 'upside-down'. The highest string on the page is the thinnest string that is on the bottom of the guitar you are playing. The number in the circles off to the left indicate string number. Numbers in circles are almost always strings. The vertically written TAB just to the right of the string numbers act as a 'clef'. You may or may not see either the numbers in the circle or the word TAB on specific sources. Sometimes, you'll see the string names rather than the numbers in circles. You can check online legends for specifics for any source.
Sometimes the rhythm of a song will be written into the tab, yet this is rare. If tab is coupled with music notation, you can interpret the rhythm from the staff above it. If the rhythm isn't shown, it is assumed that you have a recording of the song, or are familiar with it enough to interpret & play it. Keep in mind that many tabs on the internet can have mistakes. It's a good idea to learn how to listen to songs & figure them out. Everyone can do it.
The guitar as we know it today has only been around for around 210 years, so early tab wasn't for guitar, but rather the lute & vihuela.
Tab is an alternative to music notation. Typically, if you want to learn to play songs, you will need to know how to read tab - as many songs are formatted in it.
Slurs are fretting hand articulations. They connect tones. They are a way to create legato between tones [connected & smooth]. There are 5 types: pulls, hammers, slides, bends, and vibrato. They are used extensively in soloing and chord playing.