The tide-generating force is the difference between the centrifugal force F produced by the movement of the earth around the sun and the gravitational attraction Gexerted by the sun.
The centrifugal force is the same everywhere on the earth's surface. The gravitational force is largest under the sun (at the zenith Z) and smallest at the point opposite (the nadir). The difference between F and G is thus directed away from the earth under both the zenith and the nadir. This produces two tidal bulges or high tides and a line of low tide inbetween. Continents and ocean topography modify the tidal pattern but do not change the principle.
The same principle applies to the gravitational attraction of the moon. The actual tides are the combined effect from sun and moon. The next diagram shows how this produces spring and nep tides.