How do acids help 'solubilise' compounds? I've heard that root hair cells in plants secrete acids to help 'solubilise minerals' so that they dissociate and are in ion form... this supposedly allows them to be absorbed.

How so can acids solubilise certain compounds? It must be noted: I am a student and my solubility knowledge is fairly basic. I understand that ionic compounds dissolve in water because of the water molecule and the compound's polarity, but it goes no further than that.

Thank you in advance.
There are multiple ways in which plant root and root hair cells increase the availability of nutrients and positively affect the plant’s ability to absorb nutrients from the soil.  

One of these ways is by excretion of $\ce{H+}$ ions from malaic acid. This promotes a cation exchange process that results in cationic nutrients being brought into the cell in order to maintain charge balance.  This is the process to which you are referring in your question.

Additionally, enzymes, for example phosphotases, can convert chemically unavailable nutrients, like organic phosphorus, into bioavailable inorganic phosphates.  Phosphate uptake is a case in which acidic soils actually inhibit the availability of this nutrient to plants. (Annals of Botany, 112: 317 – 330, 2013)

There are also proteins excreted by root hairs that can complex metal ion nutrients like iron, facilitating the uptake of such nutrients.