what is the definition or guardianship in texas? and is there a difference between guardianship and custody?

On 10-29-09 my friend signed a paper that was notarized stated"I, Jane , give Cathy guardianship of my two daughters(daughter 1 w/DOB)and(daughter 2 w/DOB)"what exactly did Jane do?She had just lost her mother a week before & moved temporarily w/ her sister in houston.Her kids could not stay with her due to there was not enough room in the house, so her ex sister in law (cathy) offered to take them in temporily & in order to take the kids to get a flu shot she claimed she needed guardianship.On 11-5-09 Jane went to pick up her kids so that they could live with her at her dad's and Cathy refused to give them to her w/o the kids father there(he lives out of town, its unknown when he will be intown) .Cathy is 5 months into a high risk pregnancy so Jane didn't want risk her & her babies health