Ah, no wonder you don't understand these words, because they actually mean almost nothing!
Originally, it was used to rephrase something like "in otherwords" or "rather";
e.g.
xxxx toiuyori, mushiro, yyy dearu.
it is rather yyy than xxx.
(toiuka is colloquial form of toiuyori)
xxx part also can be quotation from other's statement.
A: zzz wa xxxx da.
B: ...toiuka, sorewa yyy janai?
This latter usage was somehow started being used at the beginning of conversation by young people several years ago.
To me it sounds abrupt (makes me wonder "what are you referring to?") but now it's quite commonly used espcially when they want to change the topic or just when they want to say something (regardless the new statement is relevant or not to its preceding conversation/topic/sentence, whatsoever).
"sa" is suffix making the sentence very casual (OK for using among friends but not very good when you want to be polite), "teka" is contracted form of "toiuka".