There are some times you may not understand quite a lot of the terms used in soccer predictions. Below are guides to all terminology in soccer betting.

1X means Home win or draw. The home team must not lose the match and can either draw or win. Some people also use X1. It means the same. 

2X or X2 means the away team must either win or draw the match. The away team mustn't lose. 

3-way means the same as 1X2. Its a situation where you pick just one outcome for the match in question. 
1 for home win
X for draw
2 for away win. 
In a 3-way selection you can only select one outcome which can be 1 for home win, X for match draw or 2 for away win. 

HT means halftime. Just like the full time matches, you can also select a 3-way (1X2) for HT matches. 
1HT for home to win at half time. 
X HT for match to draw at half time. 
2HT for away win at half time. 

GG is known as Goal/Goal
This term, some others use as BTS (both team scores) or BTTS (both teams to score)
Others refer it as Mutual Goals

OVER2.5 means 3 or more goals must result from the match irrespective of whichever team scores

Under 2.5 means the total goals that results from the match irrespective of the teams must not exceed 2. 

3+ is the same as over 2.5 goals which means 3 goals and above. 

0-2 is what some others term as under 2.5 goals. Meaning zero to 2 goals in match. 

CS is known as correct score.  
Its actually a situation where you predict the accurate outcome of scores in the match. 

DNB means draw no bet. 
Its a similar scene with x1 or x2 but the difference is, when there is a draw, you get refunded. 
1DNB means Home Draw No Bet. 
2DNB means Away Draw No Bet.