Wireless sensor networks (WSNs) have experienced enormous growth, both in terms of the technology used and their practical applications. In order to understand the features of WSNs that make the solution suitable for a speciﬁc purpose, one needs to be aware of the theoretical concepts behind and technological aspects of WSNs. In this paper, the signiﬁcance of WSNs is illustrated, with a particular emphasis placed on their demands and on understanding researchrelated problems. A review of the literature available is presented as well. Detailed discussions concerning sensor node architecture, different types of sensors used and their relevance for various types of WSNs is presented, highlighting the need to achieve application-speciﬁc requirements without degrading service quality. Multipath and cluster-based routing protocols are compared in order to analyze QoS requirements they are capable of satisfying, and their suitability for different application areas is reviewed. This survey highlights the performance of different routing protocols, therefore providing guidelines enabling each of the routing techniques to be used, in an efficient manner, with factors such as speciﬁc network structure, protocol operation and routing path construction taken into consideration in order to achieve better performance.