"ci" is palatalized, it's softened. 'c' here is not really the same sound as the 'c' in 'co'.
Listen to "C Ć=CI CZ" in section 2 here: http://popolskupopolsce.edu.pl/lekcja/1/MAZOWIECKIE
In general "this/these" is used when describing objects relatively near to you and "that/those" is used to describe objects more far away. In plural form you also have to differentiate between personal and non-personal masculine. Here are the different cases:
Ten (masc.), ta (fem.), to (neutr.) = "this"
Tamten (masc.), Tamta (fem.), Tamto (neutr.) = "that"
Ci (only personal-masc.), te (fem., neutr. & non-personal masc.) = "these"
Tamci (only personal-masc.), Tamte (fem., neutr. & non-personal masc.) = "those"